I was wondering the same thing..

Like others have said, it really depends on my mood and energy. If I am tired I usually sit and spin, but if I have energy I sit down and hammer it up the hills, or I stand and mash. Standing and mashing work better up really steep but short inclines, but sitting and hammering it works best for longer, less steep inclines. If I had to choose one position that I like the most it would be standing and mashing.